Here's a place where I can post my thoughts on new papers, provide updates on my projects, and post info that will eventually be on my website The Theropod Database - http://theropoddatabase.com/ . It will center on theropods, but may delve into other topics as well such as phylogenetics.

Thursday, January 6, 2011

"Dachongosaurus" - Zhao's nomina nuda part 2

The first entries in this series are sauropodomorphs, so repeat some information from the first post of the year (including photos for completeness sake). Remember general references are given in part 1.

Specimen of "Dachongosaurus yunnanensis" (after Zhao, 1985).

"Dachongosaurus yunnanensis" Zhao, 1985
"Dachungosaurus yunnanensis" Zhao, 1985Etymology- Dachong refers to the red color of the beds it was found in, while the species name refers to the province it was discovered in.Sinemurian, Early Jurassic
Shawan Member of the Lufeng Formation, Dafongtian, Yunnan, China
Material- (~9.7 m) partial skeleton including at least nine dorsal vertebrae (~118 mm), seventeen dorsal ribs, femur (~955 mm)Comments- "Dachongosaurus" is used in the text, while "Dachungosaurus" is used in the plate caption. Which will be used (if either) if it is eventually officially named is unknown.
A photo of the skeleton in situ is in Zhao (1985). Li et al. (1998) include Dachongosaurus yunnanensis in a faunal list. The length is estimated based on comparison with Jingshanosaurus, using the femoral length estimated from the photo.Relationships- Stated by Zhao (1985) to be a basal sauropod with some derived features. Lambert (1990) listed it as a cetiosaurid, which Olshevsky (1991) also referred it to provisionally. Glut (1997) merely listed it as Sauropodomorpha incertae sedis. While few details are available from the photo, the femur appears to be strongly sigmoidal unlike the condition in sauropods. While the size is large for a non-sauropod, it is approached by some taxa such as Jingshanosaurus (femur 880 mm). It may in fact be a Jingshanosaurus specimen, though the material itself has not yet been described (contra the possibility alluded to on Wikipedia), as the Jingshanosaurus holotype is positioned differently and Xixiposaurus is much smaller. For now I recommend placing it as Plateosauria incertae sedis, as the large size is at least unknown in more basal sauropodomorphs. Reference- Li, Zhang and Cai, 1998. The Characteristics of the Composition of the Trace Elements in Jurassic Dinosaur Bones and Red Beds in Sichuan Basin. Geological Publishing House, Beijing. 155 pp.

6 comments:

Yes, its really big but its size not totally unheard of amongst non-sauropod sauropodomorphs. The biggest Plateosaurus femur ('Pachysaurus wetzelianus') reaches 98 cm, the juvenile Aardonyx femur is getting close to 70cm so I would expect the adult to reach a similar size, and there are little bits and pieces of even larger non-sauropods in the lower Elliot (actually currently under study so more will appear later).

Insights? hmmmm. The neural spines look like they might be low (or just plain busted off). If the former then that backs up your assessment of a taxon basal to the advanced straight-limbed forms like Melanorosaurus and Sauropoda. Other than that, nope - there isn't much you can do with it.

Here I place the larger femora Prosauropoda I know, from the bottom up. Seniors who have the sign?, are calculated by me, very precise and careful.

1. Gresslyosaurus robustus. TS EUFemur 90 cm

2. Plateosaurus sp. TS EUFemur 91 cm

3. TS Gresslyosaurus EU ingensFemur 98 cm

4. Pachysaurus wetzelianus TS EUFemur 98.7 cm

5. Euskelosaurus browni JI AFFemur 1 m?

6. Camelotia borealis TS EUFemur 1.04 m "

7. "Thotobolosaurus mabeatae" TS AFFemur 97 cm-1 m?

8. Yunnanosaurus youngi JM ASFemur 1.1 m?

9. Prosauropod Scotland TS EUFemur 1.1 m?

10. "Riojasaurus"sp. TS SAFemur 1.28 m?

11. Pachysaurus giganteus TS EUFemur 1,415 m?Surprising and strangely ignored prosauropod giant despite being known for decades. His metatarsals from 41 to 52 cm above the total wetzelianus Pachysaurus (33 to 36 cm) by 44% in size. Rivals the size of the largest sauropod from the TS, a probable "Isanosaurus"adult, though it would be less burdensome.